The present invention is directed to an improved capacitor. More specifically, the present invention is directed to a capacitor comprising channels for directing flex cracks in a benign direction wherein the function of the capacitor is not hindered.
Capacitors are well known in the art of electrical components. Capacitors typically comprise parallel plates with a dielectric there between. The parallel plates act as charge collectors and sources. The function of capacitors is well known and further discussion is not warranted herein.
Capacitors are passive elements that are added to circuitry with the primary function of being a source of energy for circuit functionality. Capacitors are primarily mounted onto circuit traces as a reserve of energy, and in themselves do not typically contribute to the circuit charge or discharge path.
Multilayer ceramic capacitors (MLCC) are used in a variety of electrical applications including automotive products, aerospace products, heavy equipment and military applications, as examples. Typical applications include telemetrics, entertainment systems, drive control systems, environmental control systems, console instrumentation, communication systems, weapons fire control systems, detection systems and the like. Many applications involve particularly harsh environments including extreme temperature and humidity excursions, vibrations, jolting, and other potentially harmful activities. All of these conditions can lead to substrate flexing which places considerable stress on the capacitor. The stresses due to flexing typically lead to failures in the insulation and are referred to as insulation failure (IR) losses.
Flex cracks, which are a common problem in MLCC's, often lead to a loss of both capacitance and IR. Decreases in IR is considered to be the most severe issue with regards to the percentage of diagnosed capacitor failures, severe cases lead to “short-circuit” and circuit failure. They can occur in many areas of the lifecycle including manufacturing, device assembly, module assembly and during the ultimate application or use. Flex cracks lead to a myriad of problems from manufacturing losses to complete device malfunction with many failure modes there between. As there is no method for 100% electrical or visual testing of this fault, most problematic is the flex crack whose failure is delayed to the point where field failures occur.
Various designs have been described to avoid flex cracks. These include open-mode, floating electrode and flexible termination capacitors. The open-mode designs use wide end margins to prevent the crack from propagating into the active area. Floating electrode capacitors use coplanar non-contacting electrode plates with non-terminated plates interleaved between the planes. Flexible terminations create an elastic connection to the substrate, or printed circuit board, so that small displacements at the termination point on the substrate can be withstood without cracks occurring in the capacitor.
Eliminating flex cracks has proven to be a very difficult task using the techniques currently employed in the art. Furthermore, the methods described are design specific therefore requiring a different method of crack failure mitigation with each new capacitor design. The present invention provides a method of mitigating the impact of flex cracks which is not design specific.